Intangible Assets and Goodwill (Narrative) (Details) $ in Millions	Sep. 30, 2019 USD ($)
Goodwill [Line Items]
Amount of fair value in excess of carrying amount	$ 2,200
Percentage of fair value in excess of carrying amount	33.00%
Atlantic Aviation
Goodwill [Line Items]
Amount of fair value in excess of carrying amount	$ 1,900
MIC Hawaii
Goodwill [Line Items]
Amount of fair value in excess of carrying amount	280
IMTT
Goodwill [Line Items]
Amount of fair value in excess of carrying amount	$ 20
Increase in discount rate	0.25%
Amount of fair value decrease due to a 0.25% discount rate increase	$ 70